The goal of the proposed research is to examine how marital satisfaction is linked to partners' wellbeing. While it has been well established that marital satisfaction is strongly linked to partners' mental health, the underlying pathways are not well understood. The proposed study will attempt to delineate the pathways involved by using longitudinal and behavioral genetic techniques. This research will examine how: change in spouses' wellbeing influences change in partners' marital satisfaction and wellbeing over time (Specific Aim 1); assortative mating for wellbeing accounts for partners' marital satisfaction (Specific Aim 2); and parental warmth in childhood accounts for the association between marital satisfaction and wellbeing in adulthood (Specific Aim 3). To achieve the stated research goals, the proposed study is motivated by the following three training aims: to develop and apply theoretical and didactic skills in lifespan development (Training Aim 1); to learn and apply skills in longitudinal data analytic techniques (Training Aim 2); and to learn and apply skills in assortative mating modeling techniques (Training Aim 3). The proposed research will use existing data from two complimentary samples: the Nonshared Environment in Adolescent Development (NEAD; R01MH43373, R01MH48825, and R01MH59014) project: a longitudinal sample of spouses in middle and older adulthood and the Twin and Offspring Study in Sweden (TOSS; R01MH54601): a cross-sectional sample of middle adult same-sex pairs of twins and their spouses or partners. In line with Strategic Direction A-1 of the National Institute on Aging (NIA), findings will help to identify multiple pathways through which positive social interactions are linked to wellbeing, thus helping to identify intervention targets to improve adults' mental health and quality of life (2008).